This study is designed to look at the secretory pattern of endogenous PTH an PTHrP in subjects with primary hyperparathyroidism (HPT) and those with humoral hypercalcemia of malignancy (HHM), respectively. Subcutaneous intermittent injection of PTH and PTHrP to humans show some dissimilarities from the clinical manifestations caused by the endogenous over production of the respective hormones. One of the possible mechanisms by which this can happen could be explained by a difference in the mode of secretion (e.g., pulsatile versus continuous) of these hormones. This study is aimed to answer this question.